The town of Progreso, Mexico, sits on a limestone shelf that falls away extremely gradually as it gets further out to sea. As a result, when they built a pier to allow cruise ships to dock here, it had to be long. Really long. Measuring a phenomenal 6.5 kilometers (4 miles), this is the world’s longest pier. The original pier was completed in 1942, and despite being little more than a two-lane highway, is actually quite nice looking seen from the beach. In this satellite shot you can clearly see where the original construction ends, and the more…